Integrated circuits form the basis for many electronic systems. An integrated circuit may include a vast number of transistors and other circuit elements that may be formed on a single semiconductor wafer or chip and may be interconnected to implement a desired function.
Many modern electronic systems are created through the use of a variety of different integrated circuits; each integrated circuit performing one or more specific function. For example, computer systems may include at least one microprocessor and a number of memory chips. Conventionally, each of these integrated circuits are formed on a separate chip, packaged independently and interconnected on, for example, a printed circuit board (PCB).
As integrated circuit technology progresses, there is a growing desire for a “system on a chip”, in which the functionality of all of the integrated circuit devices of the system are packaged together without a conventional PCB. In practice, various “system modules” have been introduced that electrically connect and package integrated circuit devices which are fabricated on the same or on different semiconductor wafers. Initially, system modules have been created by simply stacking two chips, e.g., a logic and memory chip, one on top of the other in an arrangement commonly referred to as chip-on-chip structure. Subsequently, multi-chip module (MCM) technology has been utilized to stack a number of chips on a common substrate to reduce the overall size and weight of the package, which directly translates into reduced system size.